Cortisol is a central player in stress associated diseases such as depression, chronic pain syndrome, neurodegenerative disorders (Knezevic et al. 2023), and adrenal gland disorders such as Addison's disease (Henry, Thomas, and Ross 2021). Cardiovascular diseases entail elevated risks for Alzheimer’s disease. Fittingly, cortisol can be associated with both cardiovascular diseases and Alzheimer’s disease (Toledo et al. 2012), however the connection between chronic stress and Alzheimer's, especially with regards to the immune system, is actively being investigated, due to not being completely clear (Jones and Gwenin 2021).
The rapid and affordable detection of the stress hormone cortisol would make the diagnosis and control of these conditions much easier. Despite many researchers dedicating their efforts to developing a wearable, continuous cortisol measuring device, Inspired by subcutaneous blood sugar-monitoring devices used by diabetes patients we plan to develop an arm patch for cortisol measurements in interstitial fluid. Having measurements at least once an hour over a period of 24 or more hours would allow to monitor the circadian rhythm of cortisol fully automated.
Initially, the point-of-care for Addison’s disease, which is a disfunction of the adrenal glands and results in dangerously low cortisol levels (Saverino and Falorni 2020), was the start of this project.
We picked it as a working problem, as it resets cortisol levels in simple terms to zero and decided to develop our device for a diagnostic and monitoring purpose aligned with the circadian rhythm. Many current approaches for detection and monitoring include electrochemical and optical biosensors in mostly sweat and saliva (Karachaliou et al. 2023; Vignesh et al. 2024). By using said interstitial fluid, we want to eliminate the problems of: permanent sweat supply and cortisol build-up from old sweat blocking the sensors (Vignesh et al. 2024), or continuous access to saliva which could be annoying and uncomfortable for patients during day-to-day activities.
The glucocorticoid receptor (GR) specifically binds cortisol (Simmons et al. 2008) and naturally occurs in the cytoplasm associated with heat shock protein 90 and 70 (Fadel et al. 2023). Using GR mounted to a gold electrode we want to detect cortisol binding via the conformational change of GR, which shifts the electric potential of the gold. The ligand binding is measured with electrochemical impedance spectroscopy (EIS) that measures the signal of the electrode taking capacitance, and resistance into account (Lazanas and Prodromidis 2023). Once verified, we want to develop the arm patch using these same principles.
Stress is common. However, especially chronic stress bares risks for the progression of various chronic diseases (Knezevic et al. 2023). Elevated cortisol is associated with stress and thus serves as a biomarker. There is already prior work in the direction of continuous cortisol monitoring as it has many applications including stress control (Ok et al. 2024), and also for Addison’s disease patients, who in contrast have reduced levels of cortisol and require supplementation (Henry, Thomas, and Ross 2021).
Our goal is to develop a device that helps to be aware and mindful of personal stress levels, allowing the individual for assigning an objective numerical value to the subjective feeling of being stressed, and promotes activities to destress and live a healthier life. The long-term effect of stress monitoring should be to counter development of stress related conditions. Additionally, we hope to aid patients with Addison’s disease to monitor cortisol levels during supplementation therapy and allow for adjustment toward the circadian rhythm that would occur in a healthy person’s body. With the development of a wearable continuous measurement device the next step would be the advancement with an additional function to supply medication, thus automatically performing the adjustment to the natural cortisol circadian rhythm.